The present invention relates to electrically operated thermally actuated valves, and particularly relates to such valves which are employed for controlling the flow of gaseous fluid to a fuel burner. Thermally actuated gas valves are commonly employed in residential heating furnaces and appliances such as cooking ovens, ranges, and clothes dryers.
Thermally actuated gas valves for fuel burners for the aforementioned applications typically employ a resilient poppet mounted on the end of an arm which is deflected to close the poppet against the valve seat for controlling flow to an outlet port. The more common design employed for valves of this type utilizes bimetal material for the deflectable arm; and, an electrical resistance heating coil is energized to heat a portion of the arm to cause the bimetal to deflect as desired for opening and closing the valve.
Heretofore, gas burner valves employing a bimetal arm for mounting the valve poppet have also been configured to have a portion of the poppet arm constructed with the bimetal material reversed to provide deflection in the opposite sense for a given temperature change to thereby neutralize the deflection caused by changes in ambient temperature. Typically, the root or anchored portion of the poppet arm is surrounded by the heating coil and comprises an "active" portion of the poppet arm. The outboard portion of the arm is however, not directly heated by the coil and is therefore capable of providing for ambient temperature compensation if reversed with respect to the active portion. When the heater coil is energized to open the valve, the heated "active" portion of the bimetal self-heats the compensating outboard portion of the bimetal arm and causes undesired overcompensation. If the undesired overcompensation is great enough, the valve can literally be prevented from opening or closed again after being opened while the heater coil remains energized.
Thus it has long been desired to find a way or means to provide ambient temperature compensation for an electrically actuated thermally responsive valve which is not adversely affected by the active heating for opening the valve which is easy to incorporate into the manufacture and assembly of the valve, while maintaining the overall low manufacturing costs commensurate with the bimetal construction of the valve poppet arm.